Dual Dielectric Metasurface for Simultaneous Sensing and Reconfigurable Reflections

TL;DR

The paper tackles the challenge of enabling simultaneous sensing and reconfigurable reflections in reconfigurable intelligent surfaces (RIS) for ISAC-enabled wireless systems. It proposes a dual-dielectric, interleaved hybrid unit-cell architecture that houses two sensing arrays sharing a phase center, combined with a sub-wavelength reflective array of split-ring resonators and a load-tuning matrix. Full-wave simulations around $5.5$ GHz demonstrate effective sensing-to-reflection routing, per-cell phase control via SP4T switches, and metamaterial-like properties including a negative real refractive index. The work offers a path toward dual-functional RISs that can enhance channel estimation and adaptive beamforming in 6G networks, with potential impact on ISAC, localization, and dynamic wireless environments.

Abstract

This paper presents a novel dual-functional hybrid Reconfigurable Intelligent Surface (RIS) for simultaneous sensing and reconfigurable reflections. We design a novel hybrid unit cell featuring dual elements, which share the same phase center, to support both intended functionalities, with the antenna being miniaturized via a high dielectric material approach. The hybrid unit cell has a size of one eighth of the wavelength forming the foundation of an innovative metasurface that incorporates a sub-wavelength reflecting array of split-ring unit cells integrated with a load-tuning matrix. In particular, two interleaved sensing arrays of half-wavelength spacing, orthogonal polarization, and quarter-wavelength offset are embedded within the proposed dual-functional RIS, each tasked to sense the channel parameters towards one of the end communication nodes wishing to profit from the surface's reconfigurable reflections. Our full-wave simulations, indicatively centered around the frequency of $5.5$ GHz, showcase the promising performance of both designed hybrid unit cells and reflective split-ring ones.

Figures (9)

• Figure 1: The proposed HRIS architecture consisting of our hybrid unit cells for simultaneous sensing and reconfigurable reflections (Fig. \ref{['fig:hybridcell']}) interleaved with split-ring unit cells offering additional reconfigurable reflections (Fig. \ref{['fig:Split']}). The black and red hybrid unit cells indicate cell grouping into two separate signal feeders (e.g., reception RF chains) so as to enable dual sensing operation.
• Figure 2: The proposed hybrid unit cell of size $\lambda/8$ at $5.5$ GHz incorporating a ring antenna element with a central circular disc antenna of $\lambda_g/4$, capable of realizing simultaneous sensing and reconfigurable reflections.
• Figure 3: The proposed hybrid unit cell with an SP4T switch and an integrated-circuit controller.
• Figure 4: The designed split-ring unit cell of size $\lambda/8$ at $5.5$ GHz capable of reconfigurable reflections.
• Figure 5: The $S$-parameters of the designed hybrid unit cell using Floquet ports.